A method for blowing sand into sand mounds is disclosed in U.S. Pat. No. 2,779,074. According to this publication, the blowing-in operation, that is carried out intermittently or stepwise, is terminated when the pressure in the mould chamber has risen up to a certain value. Apparently, this is primarily a safety measure, but the possibility cannot, of course, be ruled out that the selected pressure corresponds to a certain degree of filling of the mould chamber.